How are operator methods static if they operate on instances?-CodePudding

class Program {
    static void Main() {

        test b=new(2), n = new(5);
        test bh = b   n;

    }
}


class test {
    public test(int h) {
        i = h;
    }

    public int i { get; }

    public static test operator (test i, test j) {
        return new test(i.i   j.i);
    }
}

This question is probably silly but I desparately need an answer for It.

How are operator methods static if they operate on instances?
I mean I say b n which clearly are instances

CodePudding user response：

This is a compiler trick. When it encounters the expression b n, it first determines that an overloaded operator exists and calls it with test.operator (b, n). I.e., the instances are passed as parameters to the static method.

Of course, this is an invalid C# syntax, as operator is an invalid identifier. In reality, the compiler creates this IL code:

call class test test::op_Addition(class test, class test)

The full Main method:

.method private hidebysig static
    void Main () cil managed 
{
    .maxstack 2
    .locals init (
        [0] class test,
        [1] class test,
        [2] class test
    )

    IL_0000: nop

    // test b = new(2);
    IL_0001: ldc.i4.2
    IL_0002: newobj instance void test::.ctor(int32)
    IL_0007: stloc.0

    // test n = new(5)
    IL_0008: ldc.i4.5
    IL_0009: newobj instance void test::.ctor(int32)
    IL_000e: stloc.1

    // test bh = b   n;
    IL_000f: ldloc.0
    IL_0010: ldloc.1
    IL_0011: call class test test::op_Addition(class test, class test)
    IL_0016: stloc.2

    IL_0017: ret
} // end of method Program::Main